Thus, despite the running of parameters of the actions in all
renormalizable QG models might have great importance from the
theoretical perspective, its application to any kind of physics is
unclear. Since the universal QG theory in the IR is quantum GR
[1]}, we can try to explore the running using this model.
However, the use of renormalization group to explore the running
in the quantum GR is a non-trivial issue because the theory is not
renormalizable. Assuming that all massive degrees of freedom
decouple in the IR (below the Planck scale) and the physically
interesting running is in the region below the Planck scale of
energies, we arrive at the subject of effective approach to QG,
which is treated in a separate Section of this Handbook.
